Guanyl nucleotide binding proteins (G-protein) are critical components of several regulatory pathways in animal cells, specifically involved in signal transduction. Recent evidence suggests the involvement of G-proteins in the regulation of various BRM's and alterations in their function may contribute to the pathogenesis of disease. Of these G-proteins Go is present in large quantities in critical organs like vertebrate brain and heart. Its function is not known and hence these studies are aimed at understanding the role of this protein in various signal transduction pathways and its role in various malignancies associated with brain. A bovine retinal cDNA clone encoding the complete alpha subunit of Go, was isolated and sequenced, which encodes for 354a. as polypeptide (Mr 39,900). Comparison of this G-protein with other G-proteins has revealed good homology at important critical sites like GTP binding, GTP hydrolysis, and at sites ADP ribosylated by cholera toxin and pertussis toxins. Using the cDNA clone as a probe, genomic clones coding for Go alpha were obtained and characterized. Three clones encompassing 20Kb, coding for the 5' part of the coding region were characterized, and the first 3 exons were sequenced. Also, using the bovine Go alpha cDNA clone as a probe, we have obtained cDNA clones from a human brain library, clones from human brain library-Alzheimer's tissue and from a Neuroblastoma library. The cDNA clones from the normal human library are sequenced and found to have strong homology to the bovine cDNA clone.